Hello,
Welcome to ehealthforum and thanks for writing
Spotting can be due to change of the pill brand which would have caused changes in the hormonal levels.It is sometimes usual to have it when you switch from one to other.
A light and persistent vaginal bleeding like you are having most likely is suggestive of a hormonal imbalance.
The other possible causes of such disorder can be psychological stress, weight changes(obesity, anorexia, or a rapid change), exercise, drug effect etc.
progesterone deficiency.Laboratory assessment of hemoglobin, luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, T4, thyroid stimulating hormone (TSH) might be required.
Kindly visit a Gynaecologist for evaluation.If everything is normal then you might require to stop the pill intake for some time so that the body gets back to the normal state.Relax and avoid overexercising.Have healthy balanced diet and drink lots of water.
Take care!